Wyniki wyszukiwania - Biblioteka Nauki

1

The absolute chronology of Late Tripolye sites: a regional approach

100%

Diachenko A. , Harper T. K.

Sprawozdania Archeologiczne

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2016

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tom 68

81-105

EN

While numerous studies have attempted to reconcile the relative sequence of Late Tripolye sites with 14C data, results have generally conformed to the general, monolithic periodization of the Cucuteni-Tripolye cultural complex. When viewed as a multi-linear process occurring on the level of numerous interrelated regions, the development of local groups assigned to the periods CI, CI-II and CII can be shown to have a high degree of spatiotemporal variability and overlap. In this article we explore the synchronicity of interactions between groups assigned to different typo-chronological periods and propose a revised hybrid chronology for Late Tripolye development that considers both relative and absolute chronological indicators.

2

Carbon and oxygen isotope composition of organic matter and carbonates in recent lacustrine sediments

100%

Sensuła B. , Böttger T. , Pazdur A. , Piotrowska N. , Wagner R.

Geochronometria

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2006

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tom Vol. 25

77-94

EN

The distribution of stable isotopes (18O and 13C) and radiocarbon in organic materials, carbonates and water samples collected from the environment of lacustrine sediments in Gościąż Lake (Central Poland) and Wigry Lake (NE Poland) were investigated. The oxygen and carbon isotopic analysis of terrestrial semi submerged and submerged plants, shells and water samples were compared with the results of the uppermost sediments from lakes. It was found that the concentration of isotopes in different components of organic and carbonate materials in lakes and their environments are reflected in isotope composition averaging of lakes sediments, whereas the isotope composition of plants and carbonate depends on biogeochemical factors. The research carried out revealed significant variations in the distribution of the stable isotopes and 14C in different elements of lacustrine ecosystem. We have analyzed mean values and variations of 14C concentration, δ18O, δ13C of plants, carbonates and the relationship between the total content of carbon and δ13C. In the case of plants, the isotope composition depends also on the physiognomy and the photosynthesis pathway. We noticed variations in δ13C and δ18O within plant tissues, variations in δ13C among whole tissue material and alphacellulose, carbon isotopic composition of photosynthetically fixed carbon and syntaxonomic dependences and then we compared the results of isotope composition of plants and carbonates in Wigry Lake and Gościąż Lake.

3

Groups of too close radiocarbon dates

100%

Walanus A.

Geochronometria

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2006

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tom Vol. 25

5-10

EN

In the archaeological and palaeogeographical literature, it is relatively frequent to find groups of radiocarbon dates of too close values. Too close means here that the dates exhibit no other variability than that of random origin, quantified by the given measurement errors. The chi-squared statistic seems to be appropriate to test, if the given group of dates is of random variability, of larger variability (what is typical) or of too small variability. The last case is hard to explain.

4

The Effect of PDF peaks' height increase during calibration of radiocarbon date sets

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Michczyński A. , Michczyńska D. J.

Geochronometria

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2006

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tom Vol. 25

1-4

EN

Large sets of dates are often used to construct frequency distributions to investigate variability of some events, which can follow an environmental change (eg. crystallization of speleothems depends on climatic conditions). Examples of such distributions are probability density functions (PDF) created for radiocarbon dates. In order to reach reliable conclusions concerning environmental changes, we should know how to interpret these distributions. In this study, the authors discuss the problem of a possible correlation between the presence of some high, narrow peaks in the probability density function and the shape of the calibration curve.

5

Radiocarbon method in monitoring of fossil fuel emission

100%

Rakowski A. Z.

Geochronometria

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2011

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tom Vol. 38, no. 4

314-324

EN

The traditional radiocarbon method widely used in archaeology and geology for chronological purposes can also be used in environmental studies. Combustion of fossil fuels like coal, natural gas, petroleum, etc., in industrial and/or heavily urbanized areas, has increased the concentration of carbon dioxide in the atmosphere. The addition of fossil carbon caused changes of carbon isotopic composition, in particular, a definite decrease of 14C concentration in atmospheric CO2 and other car-bon reservoirs (ocean and terrestrial biosphere), known as the Suess effect. Tree rings, leaves, as well as other annual growing plants reflected the changes of radiocarbon concentration in the atmosphere due to processes of photosynthesis and assimilation of carbon from the air. By measuring radiocarbon concentration directly in atmospheric CO2 samples and/or biospheric material growing in industrial and/or highly urbanized areas where high emission of dead carbon is expected, it is possible to estimate the total emission of dead CO2 . Based on equations of mass balance for CO2 concentration, stable isotopic composition of carbon and radiocarbon concentration it is possible to calculate CO2 concentration associated with fossil fuel emission into the atmosphere. The procedure use differences between the radiocarbon concentration and stable isotope composition of carbon observed in clean areas and industrial or/and highly urbanized areas.

6

The applicability of C-14 measurements in the soil gas for the assessment of leakage out of underground carbon dioxide reservoirs

100%

Chałupnik S. , Wysocka M.

Nukleonika

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2014

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tom 59

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nr 1

3-7

EN

Poland, due to the ratification of the Kioto Protocol, is obliged to diminish the emission of greenhouse gases. One of the possible solutions of this problem is CO2 sequestration (CCS - carbon capture and storage). Such an option is a priority in the European Union. On the other hand, CO2 sequestration may be potentially risky in the case of gas leakage from underground reservoirs. The most dangerous event may be a sudden release of the gas onto the surface. Therefore, it is very important to know if there is any escape of CO2 from underground gas reservoirs, created as a result of sequestration. Such information is crucial to ensure safety of the population in areas located above geological reservoirs. It is possible to assess the origin of carbon dioxide, if the measurement of radiocarbon 14C concentration in this gas is done. If CO2 contains no 14C, it means, that the origin of the gas is either geological or the gas has been produced as a result of combustion of fossil fuels, like coal. A lot of efforts are focused on the development of monitoring methods to ensure safety of CO2 sequestration in geological formations. A radiometric method has been tested for such a purpose. The main goal of the investigations was to check the application possibility of such a method. The technique is based on the liquid scintillation counting of samples. The gas sample is at first bubbled through the carbon dioxide adsorbent, afterwards the adsorbent is mixed with a dedicated cocktail and measured in a low-background liquid scintillation spectrometer Quantulus. The described method enables measurements of 14C in mine and soil gas samples.

7

Przegląd najważniejszych prac dotyczących próby ustalenia daty spadku meteorytów oraz wieku kraterów Morasko

63%

Walesiak T.

Acta Societatis Metheoriticae Polonorum

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2021

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tom 12

129-148

EN

One of criteria suggesting impact origin may be recognition of extraterrestrial matter inside or around suspected cavities. In case of Morasko some dating results throw doubt on link between craters and meteorites. Conclusion of some past research papers was that cavities were formed about 5 ka BP (e.g. palynological investigation, luminescence dating), while more or less facts testify fall in the Middle Ages (e.g. “young” charcoal pieces in crust of meteorites or shrapnel stuck in the roots of old tree). In this paper we perform comprehensive analysis of each result and check if there exists alternative explanation. During past palynological investigation, there were examined two craters. It was concluded that beginning of accumulation of sediments in smaller cavity started 5500–5000 BP. However, pollen spectrum for largest basin was different suggesting younger age. The problem is that according to bathymetric maps, samples could be collected from inner uplift (similar feature was observed inside Porzadzie and Jaszczulty, unconfirmed impact structures yet). If we compare profiles from craters with recent research (palynological study supported by radiocarbon dating) on sediments in Lake Strzeszynskie (6 km SW from Morasko) pollen spectrum seems to be similar more to results dated to <1000 BP. Especially percentage of non-arboreal pollen for both examined Morasko craters is much higher (5 times greater than it was for layer dated to 5 ka BP in Lake Strzeszynskie). Possibility of short disturbance (related to impact) cannot be excluded, but in such case any time of event should be taken into account. For small lakes (like those filling the craters) also local conditions could play important role. Analysis of luminescence dating may also discuss past conclusions. OSL method applied for samples taken from the thin layer of sand in the bottom of largest structure (under 3,9 m of organic sediments filling the crater) suggested age 5–10 ka BP for 24 aliquots. Same number of samples (24) revealed age 0–5 ka BP (13 samples with age <3 ka BP including several younger than 1 ka BP). Older dates can be explained by partial or even no zeroing, but last contact with light (zeroing signal) of sand grains (excavated from depth of almost 4 meters under organic matter) seems that might occur only during (or shortly after) the impact. It is difficult to find convincing arguments, which can undermine initial radiocarbon dating giving age <1 ka BP for 7 of 9 samples taken from the bottom layer of organic sediments from three Morasko craters. Same issue may exist with small charcoal pieces with age <2 ka BP (and several dated to ~700 BP) discovered deep in sinter-weathering crust of meteorites. Study of charcoal particles excluded their origin during post-sedimentary processes (like forest fire) unless meteorite fragments were laying directly on the surface for period between impact and wildfire (surviving whole time inhospitable climate conditions). There are two other possible explanations of charcoals. Either they were present at location as a result of past forest fire or they were produced during impact. However, similar small charcoal pieces were discovered around many craters (Kaali, Ilumetsa, Campo del Cielo, Whitecourt) and they were successfully used to estimate maximum age of those structures. During second stage of 14C dating the age obtained from three samples (taken few centimeters above the mineral bottom) was estimated ~5 ka BP. Looking for answer why these results are so different from previous once there may be mentioned at least two options. Lake sediments is difficult matter for radiocarbon dating and results may be hundreds or even thousands years older than real age. Second explanation may be that older matter (remnant of trees, paleosoil etc.), distributed around craters during impact, could be displaced by wind, rain, erosion and trapped in the bottom of cavities. The argument, which may be also against hypothesis of impact ~5 ka BP is meteorite shrapnel stuck in the roots of old tree. Result of expertise showed, that there exists mechanical damage in the wood and the only possible explanation is that meteorite has hit living tree. Maximum age, that this type of wood may preserve (inside building) is 1,8 ka while in natural environment not more than 500 years. Anyway some further examinations should be performed. The age obtained during AMS 14C dating of 2 samples from thin layer of paleosoil, discovered under overturned flap around largest Morasko crater, was ~5 ka BP. Observation that preserved layer of paleosoil is approximately 3 times thinner than thickness of modern soil may lead to conclusion that during impact top (younger) layer of organic sediments was removed and only older part “survived” in few locations close to the rim. The conclusion of the research was that dating provides maximum age of the impact (which does not exclude much younger impact <1 ka BP) so could be considered as right explanation of past discrepancies.

8

Peculiarities of sedimentation conditions in the oxbow lakes of Dubysa River (Lithuania)

63%

Gaigalas A. , Pazdur A. , Michczynski D. , Pawlyta J. , Kleišmantas A. , Melešyte M. , Rudnickaite E. , Kazakauskas V. , Vainorius J.

Geochronometria

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2013

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tom Vol. 40, no. 1

22-32

EN

Abundant wood remains and buried trees have been found in the western part of Lithuania near Zakeliškiai and Lyduv?nai on Dubysa River (a tributary of Nemunas River) where deposits are rich in organic remnants and buried soils. In Zakeliškiai and Skiručiai sections of Dubysa River ox-bow sediments were investigated by various methods (dendrochronological, carbonate, granulometric, pollen and mollusc fauna analysis). In addition, these sections were dated using the radiocarbon method. Samples were collected from deposits of Dubysa River outcrops. The studied oxbow lakes have existed for more than 5 thousand years (from ca. 4300 BC to 1000 AD). During this period or-ganic rich deposits with trees and branches were formed in the oxbow lake. This indicates that at the end of Atlantic, during Subboreal and in the early Subatlantic periods there was a forest growing that contained mainly oaks which were falling down into an oxbow lake and later were covered by sandy and silty deposits. The granulometry of alluvial deposits, as well as the mixture of medium-grained sand and silt show different stages of Dubysa River palaeochannel formation: riverbed and oxbow lakes. Three climate warming cycles were revealed according to carbonate analysis data in all investi-gated sections. The rheophile thermophilous Holocene age molluscs species Bithynia tentaculata L., Unio cf. crassus Philipsson, Pisidium amnicum (Müller), Theodoxus fluviatilis (Linnaeus) have been found. The pollen composition and sequences have been divided into five local pollen assemblage zones (LPAZ) and described according to pollen spectra in each zone. In this way it is possible restore palaeoclimatic coherent evolution, trends and cyclical change.

9

The feasibility of measurement of radiocarbon in carbon monoxide from coal mines as a potential indicator of mine fires

51%

Luxbacher K. , Lindsay C.

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2012

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tom nr 2

27-33

EN

The current methods of fire diagnosis for inaccessible areas of coal mines, such as gob are not always definitive. In some cases, it is difficult to determine if incidents involving ignitions or smoldering have evolved into flaming minę fires. A more definitive test for fire could involve monitoring for the existence of radiocarbon -carbon-fourteen (14C) in carbon monoxide (CO). CO is produced by the Iow temperature oxidation of coal; however, since coal is millions of years old, this CO will not have any 14C in it. The only carbon that will have the modern amount of UC in it will be the CO2 that is in the air that is drawn into the mine by the ventilation system. In accordance with the Boudouard Equilibrium, an interchange can take place that converts CO2 to CO, but only at temperatures high enough to be associated with fire. If this interchange takes place, then CO would have 14C in it. The existence of 14C in CO could be a definitive indicator of fire in gob areas. This paper outlines the background associated with this theory and examines preliminary methods for testing for the presence of 14C.

PL

Aktualne metody diagnozowania pożarów w niedostępnych obszarach kopalni węgla, takich jak zroby, nie zawsze są rozstrzygające. W niektórych przypadkach, trudno jest określić, czy wypadki, w których nastąpił zapłon lub tlenie się spowodowały pożar w kopalni. Bardziej rozstrzygające badanie pożaru powinno obejmować monitoring obecności radiowęgla - węgla-14, (14C) w tlenku węgla (CO). Tlenek węgla jest produkowany przy niskotemperaturowym utlenianiu węgla, jednak, skoro węgiel ma miliony lat, tlenek węgla nie będzie zawierał 14C. Jedyny węgiel, który będzie zawierał C z obecnych czasów, będzie to CO2 obecny w powietrzu, które jest wprowadzane do kopalni poprzez system wentylacji. Zgodnie z równowagą Boudouarda może mieć miejsce zamiana, która przekształca CO2 w CO, ale tylko w wysokich temperaturach, które mogą towarzyszyć pożarowi. Jeśli taka zamiana ma miejsce, wtedy CO będzie zawierał 14C. Obecność 14C w CO mogłaby być rozstrzygającym wskaźnikiem pożarów w obszarach zrobów. Artykuł przedstawia w zarysie przesłanki powiązane z tą teorią i analizuje wstępne metody badania obecności 14C.